[purplehavoc]

There are different 5 speeds you can swap in like the nv4500,but
you will pay more for the tranny and you may need an adapter or
different t-case to get your front output on the proper side.
The old sm465 cast iron 4 speed trannys are a dime a dozen,but obviously
lack the overdrive and there is a big gap between third and fourth.

All depends on how you are going to use it and how much you want to spend.